Fluid expansion-distribution assembly

ABSTRACT

An expansion-distribution assembly for simultaneously throttling, mixing, and distributing refrigerant fluid upstream of a heat-absorbing component (e.g., an evaporator) of a heat pump system. The expansion-distribution assembly comprises a valve-nozzle adjustment device which moves a pin relative to a nozzle chamber to vary flow-characteristics therethrough. The pin is moved during operation of the heat pump system (based on, for example, pressure and temperature data) to dynamically customize the valve-nozzle for the current load of the system.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 11/739,069 filed on Apr. 23, 2007, which claims the benefit of U.S. Provisional Application No. 60/793,813 filed on Apr. 21, 2006. This application also claims the benefit of U.S. Provisional Application No. 61/251,763 filed on Oct. 15, 2009. The entire disclosures of these applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a fluid expansion-distribution assembly that expands (e.g., throttles) and distributes refrigerant just upstream of a heat-absorbing component (e.g., an evaporator) in a heat pump system.

BACKGROUND

A heat pump system can be used to control the temperature of a certain medium such as, for example, the air inside of a building. A heat pump system generally comprises an evaporator, a condenser, a compressor and a series of lines (e.g., pipes, tubes, ducts) connecting these components together so that a refrigerant fluid can cycle therethrough. Typically, the evaporator is located adjacent to or within the medium (e.g., it is located inside the building) and the condenser is located remote from the medium (e.g., it is located outside of the building).

A heat pump system can operate in a first (forward) direction, wherein it cools the temperature-controlled environment, and a second (reverse) direction, wherein it heats the temperature-controlled environment. In the forward (i.e., cooling) direction, the evaporator is the heat-absorbing component (i.e., it absorbs heat from, and thus cools, the medium) and the condenser is the heat-rejecting component (i.e., it rejects the absorbed heat to the remote location). In the reverse (i.e., heating) direction, the evaporator is the heat-rejecting component and the condenser is the heat-absorbing component. Thus, in reverse operation the condenser becomes the evaporator and the evaporator becomes the condenser.

In a heat pump cycle, refrigerant fluid enters the heat-absorbing component as a low pressure and low-temperature vapor-liquid. As the vapor-liquid passes through the heat-absorbing component, it is boiled into a low pressure gas state. From the heat-absorbing component, the fluid passes through the compressor, which increases the pressure and temperature of the gas. From the compressor, the high pressure and high temperature gas passes through the heat-rejecting component whereat it is condensed to a liquid.

A heat pump system will often include an expansion valve immediately (or almost immediately) upstream of the heat-absorbing component. When the high pressure and high temperature liquid from heat-rejecting component passes through the expansion valve, the pressure of the fluid is reduced (e.g., the expansion valve throttles the fluid) and fluid is converted to a low pressure and low temperature vapor/liquid state. This low pressure and low temperature vapor/liquid is received by the heat-absorbing component to complete the cycle.

A heat pump cycle will often also include a distributor downstream of the expansion valve. A distributor commonly includes a mixing compartment whereat fluid is evenly distributed to a plurality of tubes which feed the multiple circuits of the heat-absorbing component. A distributor can also include a flow restriction (e.g., a nozzle) upstream of its mixing compartment which increases the velocity of the fluid just prior to its entry into the mixing compartment to promote a turbulent mixing of liquid and vapor phases.

As was indicated above, when a heat pump system is operating in a first (i.e., forward and/or cooling) direction, the evaporator is the heat-absorbing component, and when it is operating in a second (i.e., reverse and/or heating) direction, the condenser is the heat-absorbing component. Thus, an expansion-distribution assembly may be positioned at the end of the evaporator which is its inlet when fluid travels in the first direction and/or may be positioned at the end of the condenser which is its inlet when fluid travels in the second direction.

When a heat pump system is operating in a direction corresponding to the expand-then-distribute direction, liquid (at a high pressure and high temperature) will pass through the expansion-distribution assembly and will be converted into a vapor/liquid (at a lower pressure and a lower temperature) for receipt by the heat-absorbing component. When the heat pump system is operating in the opposite direction, fluid passes “backwards” through the expansion-distribution assembly. A reverse flow bypass is provided so that the fluid does not have to pass (backwards) through the throttling flow path.

U.S. Pat. No. 7,302,811 to Nungesser et al. discloses a conventional arrangement for a fluid expansion-distribution assembly, where expansion of refrigerant takes place at one location and distribution takes place downstream of the expansion. After the refrigerant has been expanded and prior to distribution, the refrigerant is passed through a restricted area. In other words, the expansion is upstream and separate from the mixing and distribution functions. The expansion valve may have a valve member for varying the expansion (i.e. throttling orifice) and the distributor may have a separate valve member for varying the size of a nozzle orifice used to promote mixing of the vapor/liquid as it passes into the distribution chamber. U.S. Pat. No. 6,898,945 to Grove discloses an exemplary distributor assembly including a variable size nozzle that receive the expanded vapor/liquid from an expansion valve and facilitates mixing and distribution of the refrigerant to a plurality of evaporator channels.

SUMMARY

The present invention provides an expansion-distribution assembly for heat pumps and other refrigerant systems wherein a piston and a nozzle chamber interact to form a combination nozzle-valve that simultaneously throttles, mixes and distributes refrigerant fluid. The nozzle-valve is adjustable to provide variable valve-orifice and/or nozzle-passage to accommodate system load changes.

In an embodiment, the nozzle chamber can be oversized so that a throttle-bypass-route is not necessary for reverse flow. The valve member that is adjustable to vary the valve-orifice can be retracted sufficiently to allow for such reverse flow.

In another embodiment, the nozzle chamber can be integrated into a check valve body. The check valve body during forward flow seals a by-pass passage and in reverse flow moves to open the by-pass passage.

These and other features of the expansion-distribution assembly and/or the refrigerant or heat pump system are fully described and particularly pointed out in the claims. The following description and annexed drawings set forth in detail a certain illustrative embodiment, this embodiment being indicative of but one of the various ways in which the principles may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a heat pump system including an exemplary expansion-distribution assembly according to the invention.

FIGS. 2A, 2B and 2C are a perspective view, a sectional view and an exploded view, respectively, of the expansion-distribution assembly.

FIGS. 3A-3D are schematic views showing the interaction between a nozzle chamber and a piston.

FIG. 4 is a cross-sectional view of another expansion-distribution assembly according to the invention.

FIG. 5 is a cross-sectional view of the expansion-distribution assembly of FIG. 4 with a pin in a first position.

FIG. 6 is a cross-sectional view of the expansion-distribution assembly of FIG. 4 with the pin in a second position.

FIG. 7 is an exploded view of the expansion-distribution assembly of FIG. 4.

FIG. 8 is a perspective view of still another expansion-distribution assembly according to the invention.

FIG. 9 is a perspective view of a check valve body according to the invention.

FIG. 10 is a cross-sectional view of the expansion-distribution assembly of FIG. 8.

FIG. 11 is a cross-sectional view of the expansion-distribution assembly of FIG. 8 showing the check valve body in a closed position.

FIG. 12 is a top view of the check valve body of FIG. 9.

FIG. 13 is a cross-sectional view of the expansion-distribution assembly of FIG. 8 showing the check valve body in an open position.

DETAILED DESCRIPTION

Referring now to the drawings, and initially to FIG. 1, a heat pump system 10 according to the present invention is schematically shown. The heat pump system 10 can be used to control the temperature of a certain medium (e.g., air inside a building) and generally comprises an evaporator 12, a condenser 14, and a compressor 16. A plurality of lines 18 (e.g., pipes, tubes, ducts) connect these components so that refrigerant fluid can cycle therethrough. The evaporator 12 can be located within the medium (i.e., it can be located inside the building) and the compressor can be located remote from the medium (i.e., it can be located outside of the building).

The heat pump system 10 can operate in a first (forward) direction, whereat it cools the medium, and a second (reverse) direction, whereat it heats the medium. A reversing valve 20, or other flow-direction-determining means, can be used to select the direction of flow through the heat pump system 10. In the first (i.e., forward and/or cooling) direction, the evaporator 12 is the heat-absorbing component (i.e., it absorbs heat from, and thus cools, the medium) and the condenser 14 is the heat-rejecting component (i.e., it rejects the absorbed heat to a location outside of the medium). In the second (i.e., reverse and/or heating) direction, the evaporator 12 is the heat-rejecting component and the condenser 14 is the heat-absorbing component. In the forward mode of operation, fluid flows from the evaporator 12 to the intake compressor 16, from the discharge of the compressor 16 to the condenser 14, and then from the condenser 14 back to the evaporator 12 to complete the cycle. In the reverse mode of operation, fluid flows from the condenser 14 to the intake of the compressor 16, from the discharge of the compressor 16 to the evaporator 12, and then from the evaporator 12 back to the condenser 14 to complete the cycle.

The heat pump system 10 can additionally comprise temperature and pressure sensing lines 22 and 24. One set of sensing lines 22/24 is connected to the cycle lines 18 to sense the temperature and pressure of the gas exiting the evaporator 12 when fluid travels in the first direction. The other set of sensing lines 22/24 is connected to the cycle lines 18 to sense the temperature and pressure of the gas exiting the condenser 14 when fluid travels in the second direction. The heat pump system 10 includes at least one expansion-distribution assembly 30 according to the present invention and/or the system 10 can include two expansion-distribution assemblies 30 as shown in the illustrated embodiment. An expansion-distribution assembly 30 can be located adjacent to the end of the evaporator 12 that acts at its inlet when fluid travels in the first (i.e., forward and/or cooling) direction. Additionally or alternatively, an expansion-distribution assembly 30 can be located adjacent to the end of the condenser 14 that acts as its inlet when fluid travels in the second (i.e., reverse and/or heating) direction.

For ease in explanation, the “direction” of the system 10 will be described in relation to the expansion-distribution assembly 30 positioned adjacent the evaporator 12. The description of the expansion-distribution assembly 30 positioned adjacent the condenser 14 would be essentially the same, except that the described first direction would be considered its second (reverse) direction and the described second (reverse) direction would be considered its first direction.

Referring now to FIGS. 2A-2C, the expansion-distribution assembly 30 is shown isolated from the rest of the heat pump system 10. The expansion-distribution assembly 30 comprises a distributor body 32 and a valve-nozzle adjustment device 34. The distributor body 32 defines an inlet/outlet chamber 40, a distribution chamber 42, a nozzle chamber 44 between the inlet/outlet chamber 40 and the distribution chamber 42, and a plurality (e.g., at least five, at least ten, at least fifteen, at least twenty, etc.) of distributor tubes 46 in direct fluid communication with the distribution chamber 42. The inlet/outlet chamber 40 is adapted for connection to line 18F (e.g., it is a fitting) and functions as an inlet chamber in the first direction and an outlet chamber in the second direction.

The nozzle chamber 44 represents a restricted flow path relative to the inlet/outlet chamber 40 and it converges towards the distribution chamber 42 (this is perhaps better seen by referring briefly to FIGS. 3A-3D). The inlets/outlet of the distributor tubes 46 (which feed/drain the multiple circuits of the heat-absorbing component) surround the circumference of the distribution chamber 42. The distributor body 32 can also comprises an internally threaded opening 48 for removable (or non-removable) mounting of the valve-dispersion device 34.

The valve-dispersion device 34 comprises a casing 50, a piston 52, and a drive mechanism 54. The casing 50 has an externally threaded portion which mates with the opening 48 for attachment to the distributor body 32. The piston 52 is movable in the inlet-outlet direction (i.e., up-down in the illustrated orientation) within the casing 50, the distribution chamber 42 and/or the nozzle chamber 44. Piston movement is motivated by the drive mechanism 54 which can comprise a linear actuator (e.g., a digital linear actuator) and controlled based on, for example, information conveyed by the temperature and pressure sensing lines 22 and 24.

Appropriate seals (shown but not specifically numbered) can be provided between the distributor body 32, the casing 50, and/or the piston 52.

Referring now to FIGS. 3A-3D, the interaction between the nozzle chamber 44 and the piston 52 is schematically shown. The piston 52 comprises a conical nose portion 60 which tapers towards the nozzle chamber 44 and a stem portion 62 which extends from the nose portion 60 (and through an opening in the distribution chamber 42) for connection to the drive mechanism 54. During operation of the heat pump system 10, the piston 52 is driven to move among a minimum-flow-area position (FIG. 3A), a maximum-flow-area position (FIGS. 3B and 3C) and positions therebetween (FIG. 3D).

In the minimum-flow-area position (FIG. 3A), the piston 52 is in its most extended position and its nose portion 60 is situated well within the nozzle chamber 44. The ability to move the piston 52 to this position (and/or positions close thereto), allows the refrigerant velocity to remain high at even low loads. With conventional expansion-distribution assemblies, the nozzle geometry remains the same at low loads and the distributor may not be provided with the velocity needed to mix and distribute the refrigerant.

In the maximum-flow-area position (FIGS. 3B and 3C), the piston 52 is in its most retracted position and its nose portion 60 is situated almost entirely within the distribution chamber 42. If, when the heat pump system is operating in the first direction (FIG. 3B), the nozzle chamber 44 sufficiently provides the desired velocity for throttling, mixing and distribution, the piston nose portion 60 can simply function as a dispersion cone within the distribution chamber 42. In a dual-direction heat pump system, it may be desirable to oversize the nozzle chamber 44 so that, when the heat pump is operating in the second direction (FIG. 3C), a throttle-bypass-route is not necessary for reverse flow. That being said, the use of a bypass with the expansion-distribution assembly 30 is certainly possible.

The piston 52 can be moved into a plurality of positions between its minimum-flow-area position and its maximum-flow-area position (FIG. 3B). Piston strokes in the range of 10-40 millimeters and/or 20-30 millimeters may be appropriate, but this will vary depending upon the heat pump system characteristics, evaporator size, chamber/piston geometries and/or other factors. In any event, when the piston 52 is in its non-maximum-area positions, the piston 52 and the nozzle chamber 44 interact to form a combination nozzle-valve which simultaneously throttles, mixes, and distribute refrigerant fluid. Moreover, this nozzle-valve is adjustable, during use of the heat pump system 10, to dynamically provide a customized valve-orifice and/or nozzle-passage for the current system load.

Turning now to FIGS. 4-7, another exemplary expansion-distribution assembly according to the invention is indicated generally by reference numeral 70. The expansion-distribution assembly 70 can be used in the heat pump system shown in FIG. 1 in place of the above-described expansion-distribution assembly, or in other refrigerant systems. The expansion-distribution assembly 70 includes a distributor body 72 that includes in the illustrated embodiment a lower body 74 and an upper body 76. The upper body 76 is threaded into the lower body 74 and includes a guide bushing 78 for axially guiding a piston 80 in the distributor body 72. The lower body 74 includes a distribution chamber 82, a nozzle chamber 84, and an inlet chamber 86. The inlet chamber 86 is configured to supply high pressure refrigerant liquid to the throttling chamber 84 for expansion in the nozzle chamber to form a high velocity/low pressure refrigerant vapor/liquid that is mixed and distributed in the distribution chamber. The distribution chamber has a plurality of distribution outlets 88 for connecting to respective distribution lines 90.

In the illustrated embodiment, the nozzle chamber 84, also herein referred to as a throttling chamber or passage, is formed by an insert 92 disposed in a bore in the lower distributor body 74 and is seated on an annular shoulder at the bottom of the bore. The nozzle or throttling chamber is formed by a through hole in the insert and may be of uniform diameter (i.e. cylindrical). The insert 92 is secured in the lower body 74 by a suitable retainer, such as by a C-clip 94, and is sealed by a suitable seal such as O-ring 96.

The expansion-distribution assembly 70 further includes a valve-nozzle adjustment device 98 that includes the piston 80 having at one end a valve member in the form of a pin that is progressively tapered. The valve pin 80 is movable by a drive mechanism 100 (e.g. an actuator) into and relative to the nozzle chamber 84 to provide a variable size throttling orifice through which the liquid refrigerant is throttled for simultaneous expansion, mixing and distribution amongst the distribution outlets 88. By simultaneously expanding, mixing and distributing high velocity vapor/liquid directly into the distribution outlets, gravitational effects are decreased (relative to systems where throttling takes place in a throttling valve located remotely from a mixing valve and distribution chamber) on the high velocity vapor/liquid mixtures, thereby improving distribution across all system conditions. In the illustrated embodiment, the progressive taper of the valve pin varies the throttling orifice size as a function of the extent to which the valve pin extends into the nozzle chamber thereby to correspondingly vary the flow of liquid refrigerant through the nozzle chamber. For reverse flow, shown in FIG. 6, the pin 80 can be fully retracted out of the nozzle chamber to allow for substantially unrestricted flow of vapor and/or liquid from the distribution outlets 88 through the throttling chamber 84 to the inlet chamber 86.

The actuator 100 may be of suitable type for a given application. In the embodiment shown in FIGS. 4-7, the actuator includes an electric motor (particularly a stepper motor), a screw 102 rotated by the motor, and a nut 104 meshed to the screw and axially translated by the screw upon rotation of the screw. The nut has at its distal end a coupler for the valve pin. An anti-rotation feature is provided to prevent the translating nut from rotating with the screw. The anti-rotation feature may be of any suitable type, such as providing the exterior of the nut and interior bore of the guide bushing 78 with corresponding non-circular cross-sections.

The motor is powered and controlled by an electrical lead 106 that extends from the top of the stepper motor. The motor is controlled to vary the position of the valve pin as a function of temperature and pressure sensed by temperature and pressure sensors as previously described. The actuator is secured to the upper body part which in turn is secured to the lower body part. A suitable seal 108 is provided to seal the upper body part to the lower body part.

Accordingly, the actuator can adjust the position of the valve pin to vary the throttling orifice size to adjust for varying loads. The outlet of the throttling chamber 84 directly communicates with the distribution chamber 82 for supplying high velocity refrigerant vapor/liquid to the distribution chamber 82 for distribution to the distribution outlets 88. It can be seen that the distribution chamber 82 has an axial length considerably shorter than the axial length of the throttling chamber 84 to facilitate simultaneous throttling, mixing, and distribution of the refrigerant vapor/liquid. From the outlet of the throttling chamber to the distribution chamber, there is no further restriction of flow.

As seen from both the foregoing embodiments, there is a difference between the above-disclosed simultaneous throttling, mixing and distribution disclosed and the separate throttling and mixing/distribution in prior art systems. After expansion of the fluid, the vapor/liquid passes from the nozzle chamber to the distribution chamber without further constriction, i.e. reduction in the cross-section of flow path between the outlet of the throttling valve and inlet of a mixing/distribution valve assembly.

Turning now to FIGS. 8-13, another exemplary expansion-distribution assembly is indicated generally by reference numeral 110. This embodiment is particularly intended for use in heat pump systems or other refrigerant systems that require reverse as well as forward flow. The expansion-distribution assembly 110 includes a distributor body 112 that includes in the illustrated embodiment a lower body 114 and an upper body 116. The upper body 116 is threaded into the lower body 114 and includes a guide bushing 118 for axially guiding a piston 120 in the distributor body 112. The lower body 114 includes a distribution chamber 122, a nozzle chamber 124, and an inlet chamber 126. The inlet chamber 126 is configured to supply high pressure refrigerant liquid to the throttling chamber 124 for expansion in the nozzle chamber to form a high velocity/low pressure refrigerant vapor/liquid that is mixed and distributed in the distribution chamber. The distribution chamber has a plurality of distribution outlets 128 for connecting to respective distribution lines 130.

In the illustrated embodiment, the nozzle chamber 124, also herein referred to as a throttling chamber or passage, is formed in a check valve body 134 of a check valve assembly 132, the check valve body being movable in a passage 136 in the distributor body 112. The check valve body is normally biased by a spring 142 to a closed position whereat the check valve body seals against a valve seat 144. As shown, the valve seat can be formed by a conical surface surrounding the passage 136, and the valve body may have an annular groove retaining an O-ring 138 for sealingly engaging the valve seat. When the check valve body is closed, flow from the inlet chamber 126 can only flow through the throttling chamber 124.

As shown, the nozzle or throttling chamber 124 is formed by a through hole in the check valve body 134 having at its upper end an inlet and at its lower end an outlet, where the through hole may be of uniform diameter (i.e. cylindrical) and define a fluid passageway through the valve body. As will be appreciated, the check valve body 134, the distribution body 112 with the valve seat 144 and the spring 142 form the check valve assembly 132.

The check valve body 134 is biased in the closed or first position by the spring 142 to be sealingly seated against the valve seat 144 of the distributor body 112, and sealed by the O-ring 138. The check valve body 134 is moveable to an open or second position, shown in FIG. 13, when the pressure from the fluid flowing from the distribution lines 130 to the inlet chamber 126 overcomes the biasing force of the spring 142. When this occurs, the reverse flow acts on the valve body to move it away from the valve seat to allow flow through passage 136 in the reverse direction. To facilitate reverse flow, the valve body may be provided on its radially outer surface with one or more axially extending flutes 140 thereby allowing flow around the check valve body. The pin 120 can be fully retracted out of the nozzle chamber to allow for substantially unrestricted flow of vapor and/or liquid from the distribution outlets 128 through the throttling chamber 124 to the inlet chamber 126. The spring 142 prevents the check valve body from contacting the pin 120 when the pin is fully retracted.

The expansion-distribution assembly 110 further includes a valve-nozzle adjustment device 146 that includes the piston 120 having at one end a valve pin that is progressively tapered. The pin 120 is movable by a drive mechanism 148 (e.g. an actuator) into and relative to the nozzle chamber 124 to provide a variable size throttling orifice through which the liquid refrigerant is throttled for simultaneous expansion, mixing and distribution amongst the distribution outlets 128. By simultaneously expanding, mixing and distributing high velocity vapor/liquid directly into the distribution outlets, gravitational effects are decreased on the high velocity vapor/liquid mixtures, thereby improving distribution across all system conditions. The progressive taper of the valve pin varies the throttling orifice size as a function of the extent to which the valve pin extends into the nozzle chamber thereby to correspondingly vary the flow of liquid refrigerant through the nozzle chamber. Additionally, the pin is movable to a closed position to prevent fluid flow through the through hole from the valve inlet to the outlet during a no flow condition, for example, during a low load or when the system is shut down.

Referring again to the actuator 148, the actuator 148 may be of suitable type for a given application. In the embodiments shown, the actuator includes an electric motor 154 (particularly a stepper motor), a gear cup 156, a gear train 158, a bearing 160, the guide busing 118 (which may be also referred to as a plunger guide), and a screw 150 rotated by the motor. The gear cup is threaded into the upper body securing the plunger guide. A nut 152 is provided meshed to the screw and axially translated by the screw upon rotation of the screw. The nut has at its distal end a coupler for the valve pin. An anti-rotation feature is provided to prevent the translating nut from rotating with the screw. The anti-rotation feature may be of any suitable type, such as providing the exterior of the nut and interior bore of the guide bushing 118 with corresponding non-circular cross-sections.

The motor is powered and controlled by an electrical lead (not shown) that extends from the top of the stepper motor. The motor is controlled to vary the position of the valve pin as a function of temperature and pressure sensed by temperature and pressure sensors as previously described. The actuator is secured to the upper body part, which in turn is secured to the lower body part. A suitable seal is provided to seal the upper body part to the lower body part.

Accordingly, the actuator can adjust the position of the valve pin to vary the throttling orifice size to adjust for varying loads. The outlet of the throttling chamber 124 directly communicates with the distribution chamber 122 for supplying high velocity refrigerant vapor/liquid to the distribution chamber 122 for distribution to the distribution outlets 128. It can be seen that the distribution chamber 122 has an axial length considerably shorter than the axial length of the throttling chamber 124 to facilitate simultaneous throttling, mixing, and distribution of the refrigerant vapor/liquid. From the outlet of the throttling chamber to the distribution chamber, there is no further restriction of flow.

The above described check valve assembly, although described in the context of an expansion-distribution assembly, can be used in an expansion assembly valve to allow for reverse flow through an expansion valve without a need for a separate bypass passage as previously used in the prior art.

As will be appreciated, the check valve assembly is particularly suited for electrical expansion valves as opposed to thermostatic expansion valves. Electric expansion valves typically have a stroke of 0.300 inches while a thermostatic expansion valve has a stroke of 0.030 inches. The additional stroke provides the room that allows the check valve assembly to be integrated with the control orifice and placed “in line” with the orifice. This provides the ability for the valve to be a more compact design.

Although expansion-distribution assemblies have been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In regard to the various functions performed by the above described elements (e.g., components, assemblies, systems, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application. 

1. A refrigerant expansion-distribution assembly comprising: a distributor body including a distribution chamber having a plurality of distribution outlets for connecting to respective distribution lines, a nozzle chamber directly communicating with the distribution chamber for supplying high velocity refrigerant to the distribution chamber for distribution, and an inlet chamber on a side of the nozzle chamber opposite the distribution chamber for supplying liquid refrigerant to the nozzle chamber; and a piston movable relative to the nozzle chamber to provide a variable size throttling orifice through which the liquid refrigerant is throttled for simultaneous expansion, mixing, and distribution amongst the distribution outlets.
 2. A refrigerant expansion-distribution assembly as set forth in claim 1, wherein the piston is movable by a drive mechanism.
 3. A refrigerant expansion-distribution assembly as set forth in claim 2, wherein the drive mechanism includes a linear actuator.
 4. A refrigerant expansion-distribution assembly as set forth in claim 2, wherein the drive mechanism is controlled based on system pressure-temperature conditions.
 5. A refrigerant expansion-distribution assembly as set forth in claim 1, wherein the piston comprises a conical nose which tapers towards the nozzle chamber.
 6. A refrigerant expansion-distribution assembly as set forth in claim 1, wherein the piston is movable to a fully retracted position during reverse flow to maximize flow area.
 7. A refrigerant system comprising: a refrigerant expansion-distribution assembly as set forth in claim 1, temperature and pressure sensors for sensing temperature and pressure of the refrigerant in refrigerant flow lines associated with or extending between an evaporator and compressor, and an actuator for moving the piston for varying the size of the throttling orifice as a function of temperature and pressure sensed by the temperature and pressure sensors to adjust for system load changes.
 8. A refrigerant system as set forth in claim 7, wherein the temperature and pressure sensing lines sense the temperature and pressure of the refrigerant exiting the evaporator.
 9. A dual-direction heat pump system comprising: an evaporator, a condenser, a compressor, a plurality of lines connecting the evaporator, condenser and compressor so that refrigerant fluid can cycle therethrough in forward or reverse directions, and at least one refrigerant expansion-distribution assembly as set forth in claim 1, wherein the distribution outlets are connected to respective distribution lines leading to respective circuits of the evaporator.
 10. A dual-direction heat pump system as set forth in claim 9, wherein the drive mechanism is controlled based on system pressure-temperature conditions.
 11. A dual-direction heat pump system as set forth in claim 9, wherein the piston is movable to a fully retracted position during reverse flow.
 12. An expansion valve comprising: a body including an inlet, an outlet, a flow passage between the inlet and the outlet, and a valve seat in the flow passage; a check valve body engageable with the valve seat for closing and movable away for opening, the check valve body including a nozzle chamber extending therethrough; and a piston movable relative to the nozzle chamber to provide a variable size orifice.
 13. An expansion valve as set forth in claim 12, further including a spring that biases the check valve body to a closed position, whereat the check valve body seals against the valve seat.
 14. An expansion valve as set forth in claim 12, the check valve body including on its radially outer surface axially extending flutes to allow reverse flow to flow around the check valve body. 